Abstract: Leakage of silicon melt is monitored and touch of a seed crystal at the silicon melt is detected, and in addition, reinforcement of a vitreous silica crucible to be endurable during pulling for a long time and decrease of impurity concentration of a silicon single crystal can be expected. A method for manufacturing a silicon single crystal is provided.

Abstract: A modification process of the synthetic quartz powder, which can make a quartz glass product hardly having bubbles at the time of fusing, is provided, along with a modification process of the synthetic quartz powder and a glass product using said modified quartz powder are provided, wherein the synthetic quartz powder is kept in helium atmosphere at least in the temperature falling process, when the amorphous synthetic quartz powder produced by the sol-gel method is carried out by heat treatment in a vacuum furnace at more than the degas temperature and less than the baking temperature, wherein the highest temperature in the helium atmosphere is preferably set to from more than 700° C. to less than 1400° C., and the helium atmosphere is kept to less than 400° C.

Abstract: A carbon electrode grinding apparatus for shaping a front end of an arc discharge carbon electrode is provided with front end grinding blades configured to grind a front end surface of the carbon electrode, lateral surface grinding blades configured to grind a surface from the front end surface to a base end of the carbon electrode, and rotation means configured to rotate and drive the front end grinding blades and the lateral surface grinding blades around a rotation axis line coincident with an axis line of the carbon electrode.

Abstract: A vitreous silica crucible manufacturing apparatus includes a plurality of carbon electrodes configured to heat and melt raw material powder by arc discharge, and a value of a ratio R2/R1 of a diameter R2 of a front end of each of the carbon electrodes to a diameter R1 of a base end is set in a range of 0.6 to 0.8. Each carbon electrode has a diameter reduction portion formed at a front end position and reduced in diameter from a diameter R3 of a base end side to the diameter R2 of the front end. When a length of the diameter reduction portion is L1, the diameter of the front end is R2, the diameter of the base end is R1, an angle between the axis lines of the carbon electrodes is ?1, and X=(R1?R2)/2, a value of L1?(X/tan(?1/2)) is set in a range of 50 to 150 mm.

Abstract: A modified synthetic silica powder is produced by heating in vacuum an amorphous synthetic silica powder produced by a sol-gel process, and then cooling the heated silica powder in an atmosphere containing helium. When the modified synthetic silica powder is fused and vitrified in a process of crucible production, the resulting quartz glass crucible contains hardly any bubbles.

Abstract: A silica glass crucible used for pulling single-crystal silicon, which includes a cylindrical straight body part, a bottom part and a curved part located between the straight body part and the bottom part, wherein the curvature radius of the inner wall surface of the curved part is 100 to 240 mm. Variation of the wall thickness W of the curved part is preferably 0.1 to 1.4 mm/cm.

Abstract: A silica glass crucible for pulling up a silicon single crystal including a wall part and a bottom part is provided with a natural silica glass layer which forms at least one part of a an inner surface of the bottom part, and a synthetic silica glass layer which forms at least an inner surface of the wall part, wherein a concentration of Ca included in the natural silica glass layer is 0.5 ppm or less.

Abstract: The arc discharge apparatus comprises a plurality of carbon electrodes connected to respective phases of a power supply for heating a silica powder and causing it to fuse by generating arc discharge between the carbon electrodes. All of the carbon electrodes have a density in a range from 1.30 g/cm3 to 1.80 g/cm3, and variability in density among the carbon electrodes is 0.2 g/cm3 or less. The carbon particles that constitute the carbon electrodes preferably have a particle diameter of 0.3 mm or less.

Abstract: An arc melting high-purity carbon electrode is capable of forming stable arc at the time of arc discharge, and it is possible to produce a vitreous silica crucible with good properties, which does not cause local lack of the electrode and does not create black foreign materials or concave portions on the inner surface of the crucible. The arc melting high-purity carbon electrode is a carbon electrode used to heat and melt silica powder by arc discharge, in which the density of the carbon electrode is equal to or more than 1.60 g/cm3 and equal to or less than 1.80 g/cm3, and is formed of high-purity carbon particles having a diameter of 0.05 mm or less.

Abstract: A silica glass crucible used for pulling single-crystal silicon, which includes a cylindrical straight body part, a bottom part and a curved part located between the straight body part and the bottom part, wherein the curvature radius of the inner wall surface of the curved part is 100 to 240 mm. Variation of the wall thickness W of the curved part is preferably 0.1 to 1.4 mm/cm.

Abstract: A method of manufacturing a fused silica crucible by heating and melting a vitreous silica powder compact shaped into a mold using arc discharge of electrodes arranged around a rotation shaft of the mold, includes the steps of: arranging the electrodes in a ring shape, and setting a ratio W/R of a horizontal distance W between the electrode front end and the surface of the vitreous silica powder compact to a vitreous silica powder compact opening radius R, for at least a predetermined time during arc heating, to be in the range of 0.002 to 0.98.

Abstract: An arc discharge method of the present invention includes the steps of: heating and melting a non-conductive object by arc discharge using a plurality of carbon electrodes in an output range of 300 to 12,000 kVA; and setting a ratio of the distance between a contact position at which the carbon electrodes come in contact with each other and a front end to the diameter of the carbon electrode during the start of the arc discharge to be in the range of 0.001 to 0.9.

Abstract: A silica glass crucible having a sidewall portion and a bottom portion is provided with a first synthetic silica glass layer constituting an inner layer at least in the sidewall portion, a second synthetic silica glass layer constituting an inner layer at least in a region including a center of the bottom portion, and a natural silica glass layer constituting an outer layer in the sidewall portion and the bottom portion. A melting rate of the second synthetic silica glass layer with respect to a silicon melt is higher than that of the first synthetic silica glass layer. An aluminum concentration of the second synthetic silica glass layer is higher than that of the first synthetic silica glass layer.

Abstract: This invention provides a high purity silica crucible having low impurity concentration in its inner portion, and its production method. The crucible, in which at least each content of Na and Li being contained in the depth of 1 mm from the inside surface is less than 0.05 ppm, is given by a production method of a high purity silica glass crucible, wherein a purity of the melted silica powder layer is increased by applying a voltage between a mold and an arc electrode to move impurity metals being contained in the melted silica glass layer to the outside, when the silica crucible is produced by arc plasma heating a raw material powder of silica in an inside surface of a hollow rotary mold. The method comprises, keeping an arc electrode potential of within ±500 V during an arc melting, applying a voltage of from ?1000 V to ?20000 V to a mold being insulated to the ground, and applying a high voltage to the un-melted silica powder layer of the outside.

Abstract: A evaluation process of a vibration level at the surface of silicon melt held in a silica glass crucible is provided by setting in the vacuum furnace, the test piece of the silica glass cut out from a silica glass crucible, melting a little amount of silicon put on said piece of the glass, and measuring a vibration cycle of the silicon melt. Moreover, a silica glass crucible not causing the vibration at the surface of the silicon melt held in the silica glass crucible is also provided, wherein the vibration cycle of a silica glass of a side wall of the crucible is controlled at more than ? seconds.

Abstract: The amount of residual carbon and hydroxyl groups in a synthetic quartz powder made by a wet process is reduced by baking the synthetic quartz powder in a low pressure atmosphere. Quartz glass crucibles made using the synthetic quartz powder have low bubble contents, and are particularly suited for growing single crystals.

Abstract: The present invention provides a process and a device for producing a quartz glass crucible, which generates a stable ring-like arc and is suitable for the production of an excellent crucible having the large open diameter. In a production process and a device for producing a quartz glass crucible, wherein a quartz powder in a mould is heated to be fused by an arc discharge of the electrodes being positioned at around of a rotational axis of a mould, this invention is characterized by using an electrode structure, in which electrodes neighboring each other are positioned at regular intervals in the ring configuration, to form the stable ring-like arc being generated between the electrodes neighboring each other without generating an continuous arc between electrodes facing each other across a central portion of the ring, and heating and fusing a quarts powder.

Abstract: This invention provides a high purity silica crucible having low impurity concentration in its inner portion, and its production method. The crucible, in which at least each content of Na and Li being contained in the depth of 1 mm from the inside surface is less than 0.05 ppm, is given by a production method of a high purity silica glass crucible, wherein a purity of the melted silica powder layer is increased by applying a voltage between a mold and an arc electrode to move impurity metals being contained in the melted silica glass layer to the outside, when the silica crucible is produced by arc plasma heating a raw material powder of silica in an inside surface of a hollow rotary mold. The method comprises, keeping an arc electrode potential of within ±500 V during an arc melting, applying a voltage of from ?1000 V to ?20000 V to a mold being insulated to the ground, and applying a high voltage to the un-melted silica powder layer of the outside.

Abstract: The amount of residual carbon and hydroxyl groups in a synthetic quartz powder made by a wet process is reduced by baking the synthetic quartz powder in a low pressure atmosphere. Quartz glass crucibles made using the synthetic quartz powder have low bubble contents, and are particularly suited for growing single crystals.

Abstract: A composite crucible for pulling up monocrystalline silicon, which is superior in shape stability and suitable for a large-sized one is provided. The composite crucible is characterized in that a carbonaceous material as an outer layer and a quartz glass as an inner layer are integrally formed. Methods for preparing and regenerating a composite crucible are also disclosed.